Nanotechnology provides techniques or processes for fabricating structures, devices, and systems with features at a molecular or atomic scale, e.g., structures in a range of one to hundreds of nanometers in some applications. In particular, silicon nanostructures have attracted enormous attention in the past two decades due to their unique optical properties that cannot be observed in their bulk counterparts. Specifically for silicon photonics, various nanoscale devices can include high speed optical modulators, low loss waveguides, and even laser sources.